Aldabra giant tortoise

Published on February 14, 2015

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The Aldabra giant tortoise, sometimes called just the Aldabra tortoise, is a large reptile living on islands off the coast of Africa. One of the places this animal lives is on the Aldabra atoll, a small atoll about 250 miles (402 km) north of Madagascar and about the same distance east of Africa. This atoll gives the Aldabra tortoises their name.

Aldabra tortoises, as with many large tortoises, have large legs and large, flat feet. This helps them keep from sinking in the sand that is abundant where these animals live. Unlike many wild animals, Aldabra giant tortoises are not afraid of humans, and they seem to be indifferent to the presence of humans.

Size

As their name suggests, Aldabra giant tortoises are very big. They are, in fact, the second largest land tortoises in the world, smaller only than the Galapagos giant tortoise. Males are larger than females, but the females are sill quite large. Males normally weigh about 550 pounds (250 kg), while the females average about 350 pounds (159 kg). From the tail end of the shell to the head of the shell, males are usually about four feet (122 cm) long. Females are about 35 inches (91 cm) in the same dimension.

Some individuals can be much larger than the sizes just mentioned. One male at Fort Worth Zoological park weighed in at over 793 pounds (360 kg). This is over FOUR TIMES the weight of the average adult male human! Who would have thought that a tortoise could weight four times as much as an adult human!

Diet

Aldabra tortoises are omnivores, eating both plants and animals. These animals are grazers, much like cows. They eat whenever they are hungry and are not picky eaters. They can extend their neck to allow them to reach food that is over three feet (.9 m) above the ground! Sometimes these tortoises will supplement their diet with insects and even carrion. Unlike some reptiles, Aldabra giant tortoises are unable to obtain all of their water through their food, so they must drink water regularly. In captivity they eat mainly vegetation, and in the winter when vegetation is not as common, they eat hay and kale. If fed an improper diet in captivity, Aldabra tortoises may develop bone and/or kidney disease.

Habitat

The Aldabra giant tortoise is not picky about its habitat as long as it is the right climate and has enough vegetation. Scrub forests, swamps, beaches, and plains are all home to these reptiles.

Status and threats

The IUCN lists the Aldabra tortoise as vulnerable. During the 1600s to 1800s, sailors exploring the Indian Ocean would use these tortoises as an important food source, killing them and storing their meat in the ship’s hold for later use.

Today, threats to these reptiles include habitat destruction, predators, and competition for food. The two main predators for Aldabra giant tortoises are rats and cats. You may wonder how such a large animal could fall prey to animals so much smaller that it, but remember that tortoises cannot move very fast. Goats, while not predators of these tortoises, are threats to them because they take away the tortoises’ food. Because of these threats, Aldabra giant tortoises are the only wild giant tortoises left in the area.

Mating, eggs, and young

The breeding season of Aldabra tortoises is from February to May. Mating only occurs during the early morning and late evening, which is when these animals are more active. After mating, the females lay from four to fourteen rubbery eggs in a shallow nest. Only about half of these eggs are fertilized. In captivity, the clutch size increases, ranging from nine to twenty-five eggs. In healthy populations, females may lay two clutches each breeding season.

The length of the incubation period depends largely on the temperature of the place where the tortoises are living. When the temperature is warmer, the incubation period lasts around 110 days, but in cooler climates, this period can last for up to 250 days!

Young Aldabra giant tortoises have a shiny black shell, unlike the dull gray shell that adults have. Maturity is determined by size instead of age, and these tortoises start mating when they have grown to half of their size. This is usually about twenty-five years. Research shows that as Aldabra tortoises get older, their growth rate slows.

Age

Age is hard to measure in any animal, especially one that lives a long time. In the wild, their maximum age is unknown, but it is estimated to be around 100 years and maybe even 150! Since these tortoises outlive most researchers, it is hard to find conclusive data. One zoo estimates one of their living tortoises to be 176 years old! One Aldabra giant tortoise named Adwaita was thought to be brought to a British officer as a gift in the 1700s. She lived in the Calcutta Zoo from 1875 to 2006. Adwaita was estimated to have been born in 1750, making her 255 years old when she died. If this estimate was correct, Adwaita when she died would be older that the United States is now!

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